A self-levelling suspension system for an automotive vehicle is arranged to automatically lift or lower the vehicle body over a road surface depending upon the suspended weight of the vehicle. The self-levelling suspension system is operated in a pneumatic, hydraulic or hydro-pneumatic fashion and is controlled by a fluid pressure control valve adapted to adjust the level of the vehicle body to a predetermined value. The control valve per se is operated mechanically and is, for this reason, not adapted to produce sufficiently delayed actions. When, therefore, the suspended weight of the vehicle changes as a result of, for example, a change in the number of the occupants of the vehicle, the self-levelling suspension system tends to cause the vehicle to rise or lower excessively. This will cause an inconvenience to the vehicle occupant stepping out of a standing vehicle. The present invention contemplates elimination of such a problem caused by a prior art control device for the self-levelling suspension system of an automotive vehicle.